A variety of sensor systems capable of grasping the behavior of people are proposed in the related art.
For example, there has been proposed a residence monitoring system which is a sensor system which includes a radio slave unit which a resident always carries and a human detection sensor, and grasps the behavior of the residents and nonresidents.
This residence monitoring system decides that a nonresident intrudes into a living room if a level of reception of a signal transmitted from the radio slave unit is lowered or there is a reaction in the human detection sensor. In addition, the residence monitoring system decides that the resident is not carrying the radio slave unit if there is no change in the level of reception of the signal transmitted from the radio slave unit even when there is a reaction in the human detection sensor. In addition, the residence monitoring system decides that an abnormality has occurred if the level of reception of the signal transmitted from the radio slave unit is high and there is no reaction in the human detection sensor.
The above-described residence monitoring system is configured to include a human detection sensor installed in a living room. The installed human detection sensor may impair the aesthetic appearance of the living room. In addition, the installed human detection sensor may give a resident an impression that he/she is being monitored and the resident may feel uneasy about the human detection sensor. In other words, the installed human detection sensor may be unfavorable to the resident.
In addition, the above-described residence monitoring system requires the resident to always carry the radio slave unit even in the living room, which may make the resident feel uncomfortable.